Pancreatic reg I binds MKP-1 and regulates cyclin D in pancreatic-derived cells.
BACKGROUND
The pancreatic regenerating (reg I) gene and its protein product are derived from acinar cells and are mitogenic to beta- and ductal cells. We studied the mechanism of this mitogenic response.


METHODS
ARIP (rat ductal) and RIN 1046-38 (rat beta-) cell lines were exposed to exogenous reg I in culture or transfected with a reg I expression vector. Mitogenesis was assessed by MTS assay (CellTiter 96; Promega, Inc., Madison, WI), and cellular mRNA was subjected to gene microarray analysis to determine signal transduction pathways. Yeast two-hybrid technology was then used to determine intracellular binding of reg I protein.


RESULTS
Cells exposed to exogenous reg I showed a mitogenic response; cells transfected with reg I expression vector showed inhibited growth. Microarray analysis of the former showed induction of cyclin pathways and mitogen-activated protein kinase phosphatase (MKP-1); cyclins were inhibited in the latter. Northern analysis confirmed gene induction of cyclin D1 and MKP-1; JNK was phosphorylated prior to expression of both. Yeast two-hybrid analysis confirmed a protein-protein interaction with MKP-1; this was confirmed by immunoprecipitation.


CONCLUSIONS
Pancreatic-derived cells exposed to reg I grow by activation of signal transduction pathways involving the mitogen-activated protein kinase phosphatases and cyclins, with concomitant induction of MKP-1. However, high intracellular levels of reg I lead to decreased growth, likely via a binding to and inactivation of MKP-1. Inhibition of cell growth, and possible induction of apoptosis, may lead to differentiation of these cells to other cell types.
Mueller
Cathy M
CM
Department of Surgery, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA.
Zhang
Hong
H
Zenilman
Michael E
ME
D000818:Animals; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000378:metabolism*; D054638:Dual Specificity Phosphatase 1 / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D051847:Lithostathine / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008938:Mitosis; D020411:Oligonucleotide Array Sequence Analysis; D010183:Pancreatic Ducts / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism; D014162:Transfection; D020798:Two-Hybrid System Techniques
D051847:Lithostathine; C514404:REG I receptor, rat; D011956:Receptors, Cell Surface; C497616:Reg1a protein, rat; D019938:Cyclin D1; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat